Muchun Wang, Kunihiko Yokotani*, Kumiko Nakamura, Yoshinori Murakami,
Shoshiro Okada and Yoshitsugu Osumi
Department of Pharmacology, Kochi Medical School, Nankoku, Kochi 783
- 8505, Japan
* To whom correspondence should be addressed.
Abstract: Central effects of melatonin on the sympatho-adrenomedullary
outflow were investigated in urethane-anesthetized rats. In the intact animals,
intracerebroventricularly (i.c.v.) administered interleukin-1β (IL-1β)
(100 ng/animal) slightly, but significantly, elevated the plasma level of
noradrenaline (NA), but not the level of adrenaline (Ad). Melatonin (100
μg/animal, i.c.v.) did not modulate the effects of IL-1β on plasma levels
of catecholamines. In the pinealectomized animals, however, the same dose
of IL-1β markedly elevated plasma levels of both Ad and NA, and the elevation
of Ad was more potent than that of NA. In these pinealectomized animals,
the serum level of melatonin was significantly lower than that in the sham-operated
control animals. Furthermore, the IL-1β-induced elevations of plasma catecholamines
in these pinealectomized animals were attenuated by i.c.v. administered
melatonin. These results suggest that melatonin plays an inhibitory role
in the central regulation of sympatho-adrenomedullary outflow in rats.
Keywords: Melatonin, Pinealectomy, Interleukin-1β, Plasma catecholamine,
Sympatho-adrenomedullary outflow